Useful dental compositions include compositions resulting from the admixture of two or more components. For example, self-curing and/or self-priming dental adhesives and cements often comprise two or more components, one of which initiates the curing or hardening process when brought into contact with the other component(s). Some dental compositions are also presented in multi-component form to minimize or avoid long-term storage stability concerns otherwise present if all the components were present and in contact with one another in a single container. Such components of such multi-component dental compositions are also preferably combined with one another in certain ranges or ratios to one another to yield optimal results. Examples of multi-part dental compositions include dental bonding adhesives such as those represented by U.S. Pat. No. 5,348,988 to Suh et. al, and other dental adhesive and cement compositions well-known in the art. Multi-component dental restorative systems that include a colorant in one or more of its components may also require a separation of such components until admixing in metered amounts, depending on the nature of the colorant(s) and reactivity with the other compounds and/or the curing system employed in the restorative system.
In practice, such multi-part dental compositions are mixed immediately prior to their use in order to prevent biological or chemical contamination and to preclude the mixed composition from curing or degrading before it is applied to the target surface. However, mixing of these dental compositions is often done in small quantities, and should ideally be metered with great precision to ensure that the mixed composition contains the proper proportion of the multiple components. Mixing the small volumes of these materials called for in dental restorations at the proper ratio is difficult in a clinical setting. In many cases, these dental compositions are mixed while the practitioner or technician is manipulating the target surface, or while the dental technician is at least partially occupied with attending to a patient. Metering small volumes of these two or more component systems while manipulating the restoration site in a patient's mouth can be difficult, particularly in light of the time constraints established by the curing of the materials used. Therefore, a system for providing metered doses of a plurality of flowable dental materials in desired small volumes and at specific ratios in a system easily manipulated by the dental practitioner would be greatly appreciated in the art.
Previous attempts have been made to provide metered dosage of two-part adhesive systems, such as dual lumen syringes and similar devices. However, the expense of multi-component dental compositions, as well as the small range for error that is required to achieve the ideal mixture of the multiple components renders many of these previous systems unwieldy and impractical in laboratory and clinical dental settings. For example, a two lumen syringe might meter two components in appropriate proportions if the plunger is pushed squarely, but if the user pushes with greater force on either side of the plunger, the proportion of the components will likely vary. Further, such systems do not meter out the total volume of the combined components, which can lead to waste or improper proportion if the combined components must be further mixed with another component in a particular proportion. Typically, such prior art systems are single use dispensers, requiring the clinician to discard the entire system once the contents of one or more lumen are exhausted, and require the purchase of an entirely new system to replace or vary the applied dental composition. Therefore, a dispenser that readily meters out a prescribed total volume of components in a consistent proportion would be greatly appreciated, particularly if such a system comprises a replaceable cartridge or refillable lumens.